Process and apparatus for fire fighting by detecting and locating hidden burning material and hot embers behind walls, partitions and the like

ABSTRACT

A process and apparatus for fire fighting by detecting and locating hidden burning material, such as hot embers, hot coals, hot spots and the like behind intervening optically opaque cooler obstructions such as walls, partitions, smoke, etc. by sensing the direction and relative strength of short radio waves which are generated and radiated by such hot spots. The range of radio waves which can be employed extends from approximately 1,000 megaHertz up to 40,000 megaHertz, the optimum range being from 4,000 megaHertz to 14,000 megaHertz and my presently preferred frequency of operation is approximately 8,000 to 9,000 megaHertz because this frequency (1) is sufficiently low to provide penetration of intervening opaque objects without undue attenuation; (2) is sufficiently high to provide good directivity with portable hand-held apparatus as described; and (3) is sufficiently high to avoid much of the man-made radio interference which exists today. A portable detector and locator for hidden hot spots includes a directional antenna adapted to be aimed and moved about manually and a hand-held sensitive radio receiver coupled to the antenna with an associated indicator device which gives an appropriate signal to the user indicating that a fire or hidden hot spot has been detected and located. The signal may be audible or visual and it changes in character, for example, it gets louder or more powerful or higher in pitch as the temperature of the hidden hot spot increases and also as the user approaches it so that it subtends a greater effective angle within the beamwidth of the antenna.

United States Patent Chasek Jan. 16, 1973 [54] PROCESS AND APPARATUS FOR FIRE I 3,441,851 4/]96 9 J. W. Savage ..324/1l8 X FIGHTING BY DETECTING AND 3,464,013 8/1969 Biggerstaff et a1 ..324/99 X LOCATING HIDDEN BURNING MATERIAL AND HOT EMBERS BEHIND WALLS, PARTITIONS AND THE LIKE [75] Inventor: Norman E. Chasek, Stamford,

Conn.

[73] Assignee: International Microwave Corporation, Cos Cob, Conn.

[22] Filed: Dec.9, 1969 [21] Appl. No.: 883,030

Primary Examiner.lohn W. Caldwell Assistant Examiner -Scott F. Partridge Attorney-Robertson, Bryan, Parmelee and Johnson A process and apparatus for fire fighting by detecting and locating hidden burning material, such as hot embers, hot coals, hot spots and the like behind intervening optically opaque cooler obstructions such as walls, partitions, smoke, etc. by sensing the direction and relative strength of short radio waves which are generated and radiated by such hot spots. The range of radio waves which can be employed extends from approximately 1,000 megaHertz up to 40,000

ABSTRACT {if} 353111111iiiiiiiiiiiiiiiiiiaaaa'17765;555334732 megahertz, the optimum being from e 581 Field of Search ..340/227,227 1), 228,283; 9 p fi f ff f 'F P 324/99. 100, 118,96, 105; 325/67, 364, 361, gm 9 JSS Y f'j f f 363; 250/833; 343/703, 113, 115, 100 ME; 'I f 73/355 174/35 Ms s sufficiently low to provide penetration oi intervenmg opaque ObjCClS without undue attenuation; (2) is sufficientl high to provide ood directivity with [56] References cued portable h and-held apparatus described; and (3) is UNITED STATES PATENTS sufficiently high to avoid much of the man-made radio interference which exists today. A portable detector 2,870,439 111959 Stinehelfer ..174 35 MS and locator for hidden hot spots includes a directional 2,875,435 2/1959 McMillan ....174/35 MS antenna adapted to be aimed and moved about 2,920,174 l/l960 Haagensen "174/35 MS manually and a hand-held ensitive radio receiver cou- 2,961,478 11/1960 Burns .,174/35 MS d to h antenna i an associated indicator 2977,59] 3/1961 Tanner MS device which gives an appropriate signal to the user 2976A f et "325/361 UX indicating that a fire or hidden hot spot has been de- 3'23573l 2/1966 Se.lmg ""343/H3X tected and located. The signal may be audible or 3,164,724 1/1965 Aiken ....325/67 UX 3,325,644 6II967 Frye et a1 "fins/67 UX visual and it changes in character, for example, it gets 3,465,253 9/1969 Rittenbach ..325/364 x louder or more pflwerful hlghef Pltch as the 3.129,330 4/1964 Seling .343/100 ME ux Perature 0f the hlddeh hot spot Increases and also as 3,167,714 1/1965 Seling ..325/363 x the user approaches it 80 that it subtehds a greater 3,230,532 1/1966 Whitney .,343/l00 ME UX fective angle within the beamwidth of the antenna, 3,409,827 11/1968 W. B. Goggings,.lr ..32 5/363X 6 Claims, 2 Drawing Figures W331. l A54 .32

7D OUTPUT S/Gf/FL CIRCUIT mum TOR a PATENTEDJMI 16 I915 SHEET 2 BF 2 INVENTOR. Norman E. (/2 0519/1 IIEJIOKIVEYS.

PROCESS AND APPARATUS FOR FIRE FIGHTING BY DETECTING AND LOCATING HIDDEN BURNING MATERIAL AND HOT EMBERS BEHIND WALLS, PARTITIONS AND THE LIKE DESCRIPTION During and after the fighting of a fire, it often occurs that much of the damage to the structure is caused by the necessity of chopping openings in walls and partitions in order to inspect and make sure that the fire is completely extinguished and that all of the glowing embers are completely quenched. Otherwise, the firemen may leave and then the fire will rekindle in all of its intensity. Also, during the fighting, the presence of dense smoke can obscure the location of the actual source of the fire so that it becomes necessary to aim the firehoses in a general pattern soaking down every possible exposed region of the building. This generalized soaking down can greatly increase the water damage to the structure, and the lack of precise knowledge of the site of the fire slows down the rate at which it can be extinguished.

Among the many advantages of the process and apparatus of the present invention are those resulting from the fact that the firefighter can detect and locate hot embers, hot coals, burning hot spots, and the like which are the source of the fire, through intervening optically opaque cooler obstructions such as dense smoke, walls, partitions, closet walls or doors, or even through several walls or partitions; such that a fire can even be detected and located which is spaced several rooms away from the user.

In accordance with the process of the invention as illustratively described, it is a process for detecting and locating hidden hot spots such as burning embers, hot coals and the like behind a cooler obstruction intervening between the user and the hot spot comprising the steps of sensing short wave radiation generated and radiated by the hot spot in the range from approximately 1,000 megaHertz to approximately 40,000 megaHertz and determining the direction from which the short wave radiation is coming.

The present invention in certain of its aspects provides a process for detecting and locating hidden hot spots such as burning embers, hot coals and the like behind a cooler obstruction intervening between the user and the hot spot and for determining the relative range of the hidden hot spot comprising the steps of sensing short wave radiation generated and radiated by the hot spot in the range from approximately 1,000 megaHertz to approximately 40,000 megaHertz. determining the direction from which the short wave radiation is coming by using a directional antenna and determining the relative range of the hidden hot spot by advancing the antenna toward the hidden hot spot and noting the apparent rate of increase in intensity of the short wave radiation as the antenna is advanced.

In other of its aspects, the present invention provides a portable detector and locator for detecting and locating hidden hot spots such as burning embers, hot coals, and the like behind a cooler obstruction which is located between the user and the hot spot including a directional antenna adapted to be aimed and moved about manually with a hand-held sensitive radio receiver coupled to the antenna having an associated indicator device for giving the user an indication signal that short wave radiation has been detected and for changing the character of the indication signal as the apparent strength of the radiation at the antenna varies with direction of the antenna and with advancement of the antenna toward the source.

The various objects, aspects and advantages of the present invention will be more fully understood from a consideration of the following detailed description in conjunction with the accompanying drawings, in which:

FIG. 1 is an elevational sectional view of a room and a closet in a building, with the process and apparatus of this invention being used to locate a hidden fire in a partition behind the closet; and

FIG. 2 is a schematic diagram of the hot spot detector and locator apparatus, including an antenna and sensitive short wave receiver with a hot spot detection signal indicator.

Referring to the drawings in greater detail, FIG. 1 illustrates the invention in use. A fire 10 has occured in a partition 12 behind a closet 14 having a front wall 16 with a room 18 located in front of the wall 16. Dense opaque smoke has filled the closet l4 and has also filled the room 18.

It is to be noted that under these conditions the temperatures of the smoke and of the wall 16 and the temperature of much of the partition 12 are substantially cooler than the temperature of the hot coals 20.

In practicing the process of the invention, for example as by a firefighter in the room 18, the short wave radiation generated by the hot spot formed by the hot wood coals 20 which passes through the intervening cooler visual obstructions, is sensed in the range from approximately 1,000 megaI-Iertz to approximately 40,000 megaHertz. The line of direction 22 from which this radiation is coming is determined to determine the direction of the fire.

It is a fact that hot objects such as hot coals, hot embers and similar hot spots do radiate radio frequency energy. The amount of radio frequency energy which is radiated by the hot wood coals 20 or by similar hot spots is not very great, but such radiation does occur.

Moreover, such hot spots at the base of the flames radiate most, if not all of the radio frequency energy rather than the gases in the flames 10.

I have found that by employing the short wave radiation in the range from approximately 1,000 megaHertz to 40,000 megaHertz it is a relatively quick and convenient matter to detect and locate the hot coals at the base of such fires and to locate hot embers and the like.

Short wave radio waves in this frequency range are capable of passing through wood, brick, mortar, cement, plaster, and so forth, and they are sufficiently short in wavelength to provide directional information with a portable antenna of practicable size. The presently preferred portion of this overall range, and

the reason why it is presently preferred are discussed In order to determine whether the fire is a small intense one nearby or a larger one further away, the user advances to move the directional antenna along the line of direction 22 toward the fire. If the fire is relatively close at hand, then the apparent strength of the radio signals at the antenna 32 will increase relatively rapidly as the user advances. This increase in the apparent strength occurs because the hot spot subtends a larger angle within the antenna beamwidth as the user approaches it. A corresponding change in the character of the indication from the indicator 36 shows the user that the radio signals are increasing relatively rapidly as the user advances along the line 22, and hence he knows that the source of the fire is a localized one close at hand. The apparent strength of the radio signals at the antenna is approximately inversely proportional to the square of the distance from the hot spot to the antenna, so long as the hot spot is not so large in area as to occupy the full cross sectional area of the antenna beamwidth at the particular distance involved. The apparent strength increases with (l) the temperature of the hot spot and (2) the cross sectional area of the antenna beamwidth occupied by the hot spot.

If the hot spot is so large in area that it effectively occupies the full cross sectional area of the antenna at the distance involved, then no further apparent increase in signal strength occurs as the user continues to approach the intervening obstruction. If he is still at a relatively great distance from the intervening obstruction, he has an advance warning that a massive region of combustion is present behind the obstruction. In such a massive fire case, the presence of very high intensity signals is indicated by the indicator 36.

If the strength of the radio signals do not increase very much as the user advances across the room 18, then he can conclude that the fire is relatively much further away from him.

FIG. 2 shows the fire detector and locator apparatus 30 which I have found operates to advantage. This apparatus 30 includes a directional antenna 32, which is shown as a pyramidal horn antenna which feeds into a low-gain tunnel diode amplifier stage 38. A square wave oscillator 40 modulates the power supply voltage for the amplifier stage 38 serving effectively to turn this amplifier stage 38 on and off. It causes the stage 38 to fluctuate between an on condition in which this stage 38 provides broadband low-gain amplification of, for example, 3db and a loss of minus 30 db and an off condition in which this stage 38 provides a relatively high loss of, for example, db. When the tunnel diode amplifier stage 38 is in the off condition its temperature is equal to room temperature, and the only signal appearing at its output is the signal resulting from thermal noise.

Three broad-band tunnel diode amplifier stages 42, 44, and 46 are connected in series cascaded relationship to the output of the first stage 38.

A crystal detector 48 detects the output from the fourth amplifier stage 46, and the detected signal is fed into a video amplifier 50, with the output from the video amplifier 50 being fed into a full-wave rectifier 51, the output from which feeds into a differential direct-current amplifier 52. This difference amplifier 52 feeds into an output circuit 54 which actuates the signal indicator 36.

In order to provide an effective cut-off in the response at a temperature of approximately that of room temperature, the difference amplifier 52 is provided with an adjustable response cut-off circuit 56. The reason for providing a cut-off is that objects whose effective temperatures are below room temperature might change the indication and thus might confuse the user. This response cut-off circuit 56 includes a source 58 of direct current voltage with a potentiometer 60 connected across it. A manual adjustment knob 62 moves the slidable contact 64 along the potentiometer. The voltage from the contact 64 is bucked against the direct current output from the amplifier 52, thus any objects at room temperature or below cause the same indication from the indicator 36.

The indicator 36 may be any device for providing a suitable audible or visible indicator signal such that the character of this signal changes with apparent changes in the inensity of the radio frequency energy entering the antenna 32. My preference is for an audible signal which increases in loudness or in pitch with increasing intensity of the radio signal being received. The reason for this preference is that dense smoke will not interfere with the users operation. For this purpose, the output circuit 54 is an audio oscillator, and the signal indicator 36 is a loudspeaker driven by the audio oscillator 54. If desired, the signal indicator 36 can be a meter, in which case the output circuit 54 is a meter drive circuit, but such a visible signal indicator requires the attention of the users sight.

The operation of this sensitive radio receiver 34 is as follows:

During the periods of time while the low-gain first stage 38 is turned off, (i.e. it is operating at a gain of, say, minus 20 db) the only signal being fed into the second stage 42 is that resulting from thermal noise which is always present in the first stage 38. During the intervening periods of time while the first stage is turned on", (i.e., it is operating at a gain of, say, plus 3 db) the signal being fed into the second stage 42 is a combination of this thermal noise plus the radio signal, if any, being received.

The difference amplifier 52 provides an output voltage which is a function of the difference in signal strengths appearing at the output of the video amplifier and rectifier 51 during successive periods as the first stage is turned on" and off. The stronger the radio signal being received, the greater the difference signal to be amplified, and the more intense the indication produced by the indicator 36, e.g. the sound signal increases in loudness and pitch, or in the case of a meter, the pointer moves up the scale.

Although the illustrative apparatus includes a pyramidal horn as the directional antenna 32, it is to be understood that other forms of directional antenna may be utilized such as a parabolic reflector type of antenna or a dipole array type of antenna.

In this particular example the antenna 32 has a beamwidth of approximately 10, but other beamwidths may be employed, depending upon the desired degree of directivity. If the antenna beamwidth is too narrow, then user may fail to detect small hot spots. I have found that a beamwidth in the range from 5 to 30 works to advantage and the presently preferred beamwidth is approximately 10.

The frequency of operation may be at any point in the range from approximately 1,000 megal-lertz to approximately 40,000 megaHertz. If water or moisture is present, then the frequencies near 22,000 megaHertz should preferably be avoided because significant amounts of water absorption of radio frequency energy occurs near 22,000 megaHertz.

Very effective results can be attained at any point within the range from 4,000 megal-lertz to 14,000 megal-lertz, and this is the optimum range. Within this optimum range my presently preferred frequency is approximately 8,000 to 9,000 megaHertz. The reasons are that (1) this frequency is sufficiently low to provide deep penetration of intervening objects without undue attenuation; (2) it is sufficiently high to provide good directional information with hand-held portable apparatus as described; and (3) it is sufficiently high to avoid much of the man-made radio interference which exists today.

In the portable hidden fire locator apparatus 30 as shown the sensitive battery-operated radio receiver 34 is connected directly by a rigid mechanical connection to the antenna 32 to form an integral unit. The indicator device 36 is included in this unit, and with the handle 38 on top the unit can be conveniently carried by one hand and moved about, leaving the users other hand free for other purposes.

What is claimed is:

1. A process for fire fighting by detecting and locating hidden hot spots such as burning embers, hot coals and the like behind a cooler wall or partition intervening between the user and the hot spot and for distinguishing the location of the source of the fire, including burning embers, hot coals and the like, from the flames comprising the steps of sensing short wave radiation generated and radiated by the burning embers, hot coals and the like which passes through the wall or partition in the range from approximately 1,000 megaHertz to approximately 40,000 megal-lertz and determining the direction from which said short wave radiation is coming through such wall or partition.

2. A process for fire fighting by detecting and locating hidden fire sources such as burning embers, hot coals and the like behind a cooler wall, partition or similar obstruction intervening between the'user and the fire source and for distinguishing the direction of the hidden fire source from the flames and for determining the relative range of the hidden fire source comprising the steps of sensing short wave radiation generated and radiated by the fire source in the range from approximately 1,000 rnegaHertz to approximately 40,000 megaI-lertz, determining the direction from which the short wave radiation is coming through the wall, partition or similar obstruction by using a directional antenna and determining the relative range of the hidden fire source by advancing the antenna toward the hidden fire source and noting the apparent rate of increase in intensity of such short wave radiation as the antenna is advanced.

3. A portable detector and locator for use in fire fighting by detecting and locating hidden fire sources such as burning embers, hot coals, and the like behind a cooler wall, partition or similar obstruction which is located between the user and the fire source and for distinguishing the direction of such hidden fire source from any flames associated with such fire source, including a directional antenna having a beamwidth in the range from 5 to 30 adapted to be aimed and moved about manually with a hand-held sensitive radio receiver operating between 1,000 and 40,000 megaHertz coupled to the antenna having an associated indicator device for giving the user an indication signal that such short wave radiation has been detected coming through a wall, partition or similar obstruction and for changing the character of the indication signal as the apparent strength of the radiation at the antenna varies with direction of the antenna and with advancement of the antenna toward the fire source.

4. Portable hidden fire source detector and locator apparatus for use in fire fighting by detecting and locating visually hidden fire sources such as burning embers, hot coals and the like which are positioned behind one or more cooler walls, partitions, and similar obstructions that are located between the user and the region of the fire, said apparatus including a directional antenna having a beamwidth in the range from 5 to 30 adapted to receive the short radio waves in the range from 1,000 megaHertz up to 40,000 megaHertz that are generated and radiated from the hidden source of the fire and that have passed through such obstruction, a portable, sensitive battery-operated radio receiver adapted to amplify and detect the presence of such short radio waves received by the antenna, said portable sensitive battery operated radio receiver being directly mechanically connected to the directional antenna to form an integral hand-held unit which can be conveniently held and moved about by one hand and an indicator device coupled to the output of the radio receiver for providing the user with an indication signal which varies as a function of the apparent strength of such short radio waves being received by the antenna.

5. Portable hidden fire hot spot locator apparatus for locating hot spots resulting from the fire and which are hidden behind visually opaque obstructions comprising a directional antenna adapted to receive the short radio waves which are generated and transmitted by such hot spots, a portable sensitive radio receiver coupled to the directional antenna, said receiver including a first broadband low-gain tunnel diode amplifier stage, a square wave oscillator coupled to saidfirst stage for switching said first stage effectively between low gain and high loss, a plurality of broad band tunnel diode amplifier stages connected in series cascaded relationship to said first stage, a detector stage coupled to the output of said cascaded stages, a video amplifier coupled to said detector stage, a rectifier coupled to the output of said video amplifier, a difference amplifier coupled to said rectifier, and an output circuit connected to said difference amplifier including a signal indicator for giving a signal to the user in which the character of the signal changes with apparent changes in the strength of such short radio waves being received by said directional antenna.

6. Portable hidden hot spot locator apparatus as claimed in claim 5 which includes manually adjustable means for adjusting said apparatus to give no indication of objects having a temperature below room temperature. 

1. A process for fire fighting by detecting and locating hidden hot spots such as burning embers, hot coals and the like behind a cooler wall or partition intervening between the user and the hot spot and for distinguishing the location of the source of the fire, including burning embers, hot coals and the like, from the flames comprising the steps of sensing short wave radiation generated and radiated by the burning embers, hot coals and the like which passes through the wall or partition in the range from approximately 1,000 megaHertz to approximately 40,000 megaHertz and determining the direction from which said short wave radiation is coming through such wall or partition.
 2. A process for fire fighting by detecting and locating hidden fire sources such as burning embers, hot coals and the like behind a cooler wall, partition or similar obstruction intervening between the user and the fire source and for distinguishing the direction of the hidden fire source from the flames and for determining the relative range of the hidden fire source comprising the steps of sensing short wave radiation generated and radiated by the fire source in the range from approximately 1,000 megaHertz to approximately 40,000 megaHertz, determining the direction from which the short wave radiation is coming through the wall, partition or similar obstruction by using a directional antenna and determining the relative range of the hidden fire source by advancing the antenna toward the hidden fire source and noting the apparent rate of increase in intensity of such short wave radiation as the antenna is advanced.
 3. A portable detector and locator for use in fire fighting by detecting and locating hidden fire sources such as burning embers, hot coals, and the like behind a cooler wall, partition or similar obstruction which is located between the user and the fire source and for distinguishing the direction of such hidden fire source from any flames associated with such fire source, including a directional antenna having a beamwidth in the range from 5* to 30* adapted to be aimed and moved about manually with a hand-held sensitive radio receiver operating between 1,000 and 40,000 megaHertz coupled to the antenna having an associated indicator device for giving the user an inDication signal that such short wave radiation has been detected coming through a wall, partition or similar obstruction and for changing the character of the indication signal as the apparent strength of the radiation at the antenna varies with direction of the antenna and with advancement of the antenna toward the fire source.
 4. Portable hidden fire source detector and locator apparatus for use in fire fighting by detecting and locating visually hidden fire sources such as burning embers, hot coals and the like which are positioned behind one or more cooler walls, partitions, and similar obstructions that are located between the user and the region of the fire, said apparatus including a directional antenna having a beamwidth in the range from 5* to 30* adapted to receive the short radio waves in the range from 1, 000 megaHertz up to 40,000 megaHertz that are generated and radiated from the hidden source of the fire and that have passed through such obstruction, a portable, sensitive battery-operated radio receiver adapted to amplify and detect the presence of such short radio waves received by the antenna, said portable sensitive battery operated radio receiver being directly mechanically connected to the directional antenna to form an integral hand-held unit which can be conveniently held and moved about by one hand and an indicator device coupled to the output of the radio receiver for providing the user with an indication signal which varies as a function of the apparent strength of such short radio waves being received by the antenna.
 5. Portable hidden fire hot spot locator apparatus for locating hot spots resulting from the fire and which are hidden behind visually opaque obstructions comprising a directional antenna adapted to receive the short radio waves which are generated and transmitted by such hot spots, a portable sensitive radio receiver coupled to the directional antenna, said receiver including a first broadband low-gain tunnel diode amplifier stage, a square wave oscillator coupled to said first stage for switching said first stage effectively between low gain and high loss, a plurality of broad band tunnel diode amplifier stages connected in series cascaded relationship to said first stage, a detector stage coupled to the output of said cascaded stages, a video amplifier coupled to said detector stage, a rectifier coupled to the output of said video amplifier, a difference amplifier coupled to said rectifier, and an output circuit connected to said difference amplifier including a signal indicator for giving a signal to the user in which the character of the signal changes with apparent changes in the strength of such short radio waves being received by said directional antenna.
 6. Portable hidden hot spot locator apparatus as claimed in claim 5 which includes manually adjustable means for adjusting said apparatus to give no indication of objects having a temperature below room temperature. 